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Method of preparing high-strength thin-crystal two-phase steel

A dual-phase steel, fine-grained technology, applied in the direction of manufacturing tools, heat treatment equipment, heat treatment process control, etc.

Inactive Publication Date: 2009-06-17
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] The purpose of the invention is to solve the problem of preparing high-strength fine-grained dual-phase steel in low-carbon (manganese) steel, and proposes a method based on supercooled austenite in A 3 ~ Ar 3 Multi-pass deformation between temperature ranges, a technical solution to control the dual-phase structure with strain

Method used

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  • Method of preparing high-strength thin-crystal two-phase steel
  • Method of preparing high-strength thin-crystal two-phase steel
  • Method of preparing high-strength thin-crystal two-phase steel

Examples

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Effect test

Embodiment 1

[0013] Select the low-carbon steel whose chemical composition is: 0.087%C, 1.24%Mn, 0.35%Si, and the balance is Fe. Its A was measured by thermal dilatation method 3 is 860°C, cooling rate C2 is 30°C / s, Ar 3 It is 760°C. After heating the low-carbon steel to 1200°C for 5 minutes, at 1100°C and 1000°C in the temperature range of T2~T3 respectively for 1s -1 strain rate deformation, the deformation amount of each pass is 30%, obtained as follows figure 2 The recrystallized austenite structure around 25 microns is shown. Afterwards, cool at a cooling rate of 30°C / s to 820°C in the temperature range of T4~T5, and -1 The deformation rate is 30% in two passes, the interval between the two passes is 1s, and the cooling rate is 60°C / s to room temperature, and the obtained image 3 In the fine-grained dual-phase structure shown, the average grain size of ferrite is about 3.94 microns, the average size of martensitic islands is about 2.56 microns, and the volume fraction is about ...

Embodiment 2

[0015] The chemical composition of the selected steel grade is the same as in Example 1. Heat the low-carbon steel to 1200°C for 5 minutes and then heat it at 1100°C and 1000°C in the temperature range of T2~T3 for 1s -1 strain rate deformation, the deformation amount of each pass is 30%, obtained as follows figure 2 The recrystallized austenite structure around 25 microns is shown. After that, cool down to 800°C at a cooling rate of 15°C / s and take 10s -1 The deformation rate is 30% in two passes, the interval between the two passes is 10s, and the cooling rate is 60°C / s to room temperature, and the obtained Figure 4 In the fine-grained dual-phase structure shown, the average grain size of ferrite is about 4.09 microns, the average size of martensitic islands is about 3.33 microns, and the volume fraction is about 10%.

Embodiment 3

[0017] The hot-rolled slab of ordinary low-carbon manganese steel is used, and its chemical composition is: 0.09%C, 1.4%Mn, 0.35%Si, and the balance is Fe. The original thickness of the blank is 15mm. The multi-pass reversible rolling test was carried out on a 350 four / two-high reversible hot strip experimental rolling mill, and the rolling speed used was 500mm·s -1 . The hot rolling process is: 1200°C for 30 minutes, then air-cooled to 1100°C to start rolling, two passes of rolling with a reduction of 30%, the interval between passes is 5s, and the temperature after the second pass is 1000°C about. After that, air cooling (cooling rate is about 12°C / s) to 840°C for two consecutive rolling passes with a reduction of 30%, the interval between passes is 3s, the final rolling temperature is 790°C, and water cooling after rolling. Figure 5 It is the SEM morphology of the fine-grained dual-phase structure obtained under this process. The average grain size of ferrite is about ...

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Abstract

The invention relates to a method for preparing fine-grain dual-phase steel, in particular to preparing fine-grain dual-phase steel from low-carbon (manganese) steel. This method austenitizes ordinary low-carbon (manganese) steel, obtains a fine austenite structure through multi-pass deformation in the recrystallization zone, and supercools to a certain temperature range from A3 to Ar3 at an appropriate cooling rate. The temperature is subjected to multi-pass deformation, and the strain rate is between 0.1s-1 and 30s-1. By controlling the strain of each pass, 80% to 90% of the ferrite transformation value is obtained, and then rapidly cooled or quenched to room temperature. The average size of equiaxed ferrite grains in the fine-grained dual-phase structure obtained by the above process is less than 5 microns, the volume fraction of evenly distributed martensite islands is 10% to 15%, and the average size is less than 3 microns. The process is more controllable, the structure is more uniform, and it is easy to realize on the traditional hot rolling mill.

Description

technical field [0001] The invention relates to a method for preparing fine-grain dual-phase steel, in particular to a method for preparing fine-grain dual-phase steel from low-carbon (manganese) steel. Background technique [0002] The microstructure refinement of dual-phase steel can not only promote the strength of dual-phase steel to a higher level, but also the complex phase of fine-grained structure still has mechanical characteristics such as continuous yield, high strength-to-yield ratio, and good work hardening ability. At present, the way to obtain fine-grained dual-phase steel mainly focuses on large-strain deformation, such as equal channel extrusion (ECAP) or the use of complex deformation heat treatment processes such as TMCP process with lower finish rolling temperature and deformation-induced phase transformation (DIFT). method. “Ultrafine grained dual phase steel fabricated by equal channel angular pressing and subsequent intercritical annealing” (Scripta M...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D8/00C21D11/00
Inventor 孙祖庆杨王玥徐海卫李龙飞
Owner UNIV OF SCI & TECH BEIJING
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